1. Field of Invention
This invention relates to devices that are particularly useful in the manufacture of vehicle tries and relates, more particularly, to apparatus defining an inner circumference suitable to serve as a circular surface to grasp the outer circumference of a circular, tubular or round object, usually for purposes of transferring of the grasped object between first and second locations. More specifically, this invention relates to an improved transfer ring, useful in the manufacture of vehicle tires.
2. Description of the Related Art
The manufacture of a vehicle tire commonly includes the steps of forming a tire, carcass, forming a toroidal belt and tread portion of the tire separately of the carcass, and thereafter marrying the belt and tread portion of the tire to the carcass to form a “green” tire. The green tire is thereafter treated to form the tread and various other features of the tire. Other supplementary steps, such as stitching may be performed during the course of or following one or more of the aforementioned steps.
As seen in FIG. 1, formation of a belt and tread portion (often referred to as a belt and tread “package”) of the tire is typically accomplished on a belt and tread drum 12. Such drum typically has an outer cylindrical surface, or circumference, about which one or more layers of tire belt material (comprising for example, reinforcement cords embedded in a polperic binder) are laid to define the belt and tread package. The circumference of such drum 12 is preferably capable of expanding and contracting to, for example, accommodate the removal from the drum of a completed belt and tread package which is essentially nonexpandable radially but which is flexible to the extent that when unsupported, the toroidal belt and tread package will sag under the influence of gravity. Also, desirably, the adjustable circumference of the belt and tread drum 12 enables a single drum to be used to form belt and tread packages of alternative diameters.
In the manufacture of vehicle tires, the drum upon which a tire carcass is formed is somewhat similar to the drum 12 upon which the belt and tread package is formed. Subsequent to the formation of the carcass, such carcass commonly is transferred to a tire expansion drum 14, and while the carcass remains on the expansion drum, it is overlaid with the toroidal belt and tread package.
In some instances, after the tire carcass has been formed, it may be transferred to a second stage drum, employing a transfer ring 16, and held thereon while a belt and tread package is transferred from the belt and tread drum onto the outer circumference of the tire carcass, also employing a transfer ring 16. Thereafter, the belt and tread package is married to the tire carcass.
The forces exerted by an expanding tire carcass during the process of marrying a belt and tread package to an expanded tire carcass may be very large. In the prior art, such large forces commonly have been accommodated by providing a relatively large power source for retaining the shoes of a prior art transfer ring in a radially inward position during the marrying of a belt and tread package to a tire carcass. Such larger power sources are relatively costly and tend to decrease the life time of the transfer ring due to exceptional friction and other forces experienced by the several elements of the transfer ring both during positioning of the shoes of the transfer ring and during the time when the elements of the transfer ring are being stressed by the expanding forces generated by the carcass. One consequence of the use of such larger power sources is the need for using costly stronger and/or larger sizes of materials in the construction of the transfer ring.
Typically, a transfer ring as employed in the vehicle tire manufacturing industry includes a plurality of arcuate segments (often referred to as “shoes”) which are disposed in a circular configuration and adjustable along radial directions of the circular configuration to collectively define an inwardly facing, expandable and collapsible circular working surface for grasping one of a tire carcass or belt and tread package and transferring the same for further manufacture of a tire as discussed above. Desirably, a tire transfer ring incorporates a maximum range of adjustability of diameter of the transfer ring such that the transfer ring can be used in the manufacture of a relatively large range of vehicle tire diameters. In order for the individual shoes of a transfer ring to move radially outward, the mechanism for mounting each of the shoes includes a hinge connection of the shoe to the mechanism which moves the shoe generally radial, inwardly and outwardly. This hinged connection permits the shoe to rotate freely about the hinge connection. In applicant's U.S. Pat. No. 5,635,016, rotation of the sections of multi-sectional arcuate segment (i.e. shoe) is controlled by guide plates attached to the sections of adjacent shoes and which interact with pin means on the sections of adjacent shoes to aid in maintaining the collective circular attitude of the sections of the several shoes as the diameter of the circle collectively defined by the shoes is increased or decreased in diameter. The fabrication, installation and maintenance of this type of interconnection of the adjacent shoes of the transfer ring or drum, however, are time consuming and expensive.
Further, applicant's U.S. Pat. No. 5,709,768, there is disclosed a transfer ring wherein the plurality of shoes are mounted on the outboard ends of respective arms, whose respective inboard ends are rotatably mounted on a fixedly mounted ring. The inboard end of each arm further includes a rigid bracket element which in turn, is included in a “train” of such bracket elements. The geometry and mounting aspects of these bracket elements are chosen such that upon the application of a linear force to the train of bracket elements, the arms are caused to rotate about their inboard mountings with resultant accurate movement of the outboard ends of the arms (and the shoe attached thereto) inwardly and outwardly of the longitudinal centerline of the transfer ring. Among other things, this device is limited as to the directionality of the path of the inward and outward movement of the shoes on the arms, and lacks capability for minimization of the force transferred from the shoes to the power source associated with the device.